
// https://leetcode.cn/problems/max-area-of-island/description/

class Solution
{
    int res = 0;
    int m, n;
    int dx[4] = { 0, 0, 1, -1 };
    int dy[4] = { 1, -1, 0, 0 };
    int area;

public:
    int maxAreaOfIsland(vector<vector<int>>& grid)
    {
        m = grid.size();
        n = grid[0].size();
        for (int i = 0; i < m; ++i)
            for (int j = 0; j < n; ++j)
            {
                if (grid[i][j] == 1)
                {
                    area = 0;
                    dfs(grid, i, j);
                    res = max(res, area);
                }
            }

        return res;
    }

    void dfs(vector<vector<int>>& grid, int i, int j)
    {
        grid[i][j] = 0;
        ++area;

        for (int k = 0; k < 4; ++k)
        {
            int x = i + dx[k];
            int y = j + dy[k];
            if (x >= 0 && x < m && y >= 0 && y < n && grid[x][y] == 1)
                dfs(grid, x, y);
        }
    }
};